Ford EGR Valves
Contents
1. PINC a EVP SIGNAL ri ward PINB SIG RTN VREF SIGNAL SIG RTN Substrate Housing assy Shaft Wiper assy Follows ECA valve position Figure 2 The EVP is a three pin sensor Fig 2 One pin A supplies five volts from the com puter Another pin B is the ground for the sensor and the third pin C is the signal back to the PCM The EVP sensor functions the same as most position sensors A five volt reference is sent across a resistive material As the pintle on the position sensor moves up the five volts travel across less of the resistive material This allows c Tomco Inc 1997 Tomco Tech Tips 32 more of the voltage to return to the computer As the pintle moves down the five volts travel across more of the resistive material so less of the voltage returns to the PCM See Tech Tip 19 for a more in depth look at EVP sensors SOLENOID TESTING A resistance check can be performed on the EGR solenoid s A rule of thumb for resis tance on these solenoids is EGRC EGRYV Solenoids should be 32 to 64 ohms EGR Shutoff Solenoids should be 51 to 108 ohms EVR Solenoids should be 20 to 70 ohms 100 to 135 ohms for 7 5L engines If you have any doubts about the ohm reading you receive check your service manual for the correct specifications for your vehicle A f2. TM FORD EGR VALVES OPERATING PARAMETERS The PCM monitors the Manifold Absolute Pres sure MAP Sensor the Engine Coolant Tempera ture ECT Sensor the Throttle Position Sensor TPS and the EGR Valve Position Sensor EVP to calculate the correct amount of EGR flow required The PCM then sends the appropriate signals to the EGR control solenoid s so precise control of EGR can occur The PCM will not operate the EGR valve unless it sees 1 The engine warmed up to normal operating temperature 2 TPS at partial throttle 3 TPS not at Wide Open Throttle WOT 4 MAP MAF must be indicating light or moderate load 5 A certain amount of computer clock time has to be elapsed EVP Aen The EVP is Seer the feedback to the J PCM of EGR 1 EYE O Ring position The Caer PCM monitors the A Housing EVP signal to see YK if the EGR valve is yy Return Spring opened the desired amount Diaphragm Lower Diaphragm As stated Aone the tip of the EVP Figure 1 ISSUE 32 rests on the pintle plate or on the small metal button cap on some models Fig 1 As the EGR pintle moves upward so does the pintle shaft of the EVP This change in the EVP position changes the voltage signal to the PCM The PCM uses this voltage signal as a reference of EGR flow EVP SENSOR VEHICLE HARNESS CONNECTOR EVP SENSOR CONNECTOR EVP SIGNAL PINA VREF G VREF
3. may be bad Exercise the EGR valve using a vacuum pump The base voltage should VOLTAGE Grey Black Figure 6 Tomco Tech Tips 32 return to the same value every time the vacuum is released If not it may be a sign of carbon buildup on the pintle 5 The sensor transition while exercising the EGR should be smooth with no glitches on the DVOM or the scope If not replace the sensor See electronics 101 for a view of labscope patterns 6 A resistance check can also be per formed on the EVP With the key in the off position remove the EVP connector With an acceptable meter measure the resistance between the VREF Pin A and EVP Pin C signal While exercising the EGR valve the resistance should range from 5500 ohms to no less than 100 ohms VACUUM PROBLEMS We have looked at the EGR solenoids and the EGR valve and EVP for testing and problems But there could be a low vacuum problem Check the source vacuum and make sure there are no leaks in the line to the solenoid Also make sure you check the line to the EGR valve itself In many cases the systems we have been looking at start to open the EGR valve at 1 to 1 5 in HG and only need a maximum of 4 in HG to open fully When checking to see if opening an EGR valve will make a difference in RPM we hook up a vacuum pump and apply 15 inches of vacuum This is almost 4 times as much vacuum as the EGR valve will see under normal operating co
4. and off As you can see we have set the scope voltage at 5 volts per division and the time base at a5 ms per division This pattern was captured loading the engine in drive The Scanner read about a 40 duty cycle The maximum high of this signal is 13 volts while the low voltage is 8 8 volts If you look at the on time of the signal where it drops to a low volt age it appears to be at the 40 duty cycle we Bad EVP Pattern have seen on the Scanner T K GIDE 200 S s 1 Acgs I festa si tithe t Chi Min j 4 36V jA 45ms 720ms Ch Pk Pk gomy A 42 6ms 42 3s Ch1 Pk Pk 4 24 Ch1 Max 13V Cht Min a 8 Figure 7 Figure 8 TOMGO Banc
5. nditions This might cause us to miss a par tially clogged or sticking EGR valve Apply the vacuum to the valve that it will see under normal operation to test it more accurately CODES Taking a careful look at and understand ing the codes on the Ford EGR system can help you chose the right diagnostic path For instance if a code 33 in the Key On Engine Running KOER test mode has been set this means that the EVP voltage did not change when the EVR was energized If a code 84 during the KOEO Tomco Tech Tips 32 test was not shown we know that the EVR Lets look at some of the waveforms functioned electrically This means that the associated with these EGR systems Figure 7 computer sent out the signal No sense in wast shows a pattern of a good and bad EVP signal ing time checking the signals from the computer As you can see we have set the scope voltage Take time to read the code description and scale at 1 volt per division and the time base at definition before you head off testing 250 ms per division At these settings we can get a good view of the EVP signal We have the ELECTRONICS 101 KOEO and are monitoring the EVP signal as we exercise the EGR valve As you can see by Good EVP Pattern the arrow in the bad pattern we have a drop out in the signal This is our glitch in the EVP Tek GEN 209 S s 14 Acqs e e E l signal i 2 A 45ms i 720ms ko Figure 8 shows the signal of the EVR chi Max cycling on
6. the filter on the solenoid Fig 4 EVR filter shown If this is clogged it will inhibit the venting of the solenoid Some of the EGRV solenoids have a vent hose that goes up to the throttle body Make sure this vacuum line and the port in the throttle body are not plugged Figure 4 If the vents are okay and the vacuum portion of the test just performed will not cycle correctly replace the solenoid s Figure 5 EGR EVP TESTING We have come up with a number of short cuts in diagnosing the EGR valve and EVP sensor The procedure is as follows 1 Disconnect the vacuum line to the EGR valve and connect a vacuum pump to it Fig 5 2 While holding your hand on the EGR valve apply 10 inches of vacuum If you feel the valve pop or stick the valve will have to be serviced or replaced 3 The valve should hold the 10 inches of vacuum for at least one minute If it doesn t hold vacuum either the EGR diaphragm is leaking or the EVP gasket is leaking We have seen a number of these gaskets leaking causing inter mittent codes 4 If the valve checks out okay test the EVP sensor Hook up a DVOM with a bar graph or preferably a labscope to the EVP signal wire Turn the Key On Engine Off KOEO The starting voltage should be in the range shown in figure 6 If it is not in range the EGR valve may have a piece of carbon holding it slightly open or the sensor
7. unctional test can be performed on most applications by using a Scan Tool Enter the Output State check and cycle the accelerator pedal This will turn all the solenoids on and off Using a DVOM monitor the voltage at the EGR solenoid s They should toggle from a high voltage to a low voltage Typically this is stated in the manuals and scan tools as above 10 5 volts to below 2 volts If the voltage does not toggle make sure that you have system voltage on the power side of the connector If system voltage is present and the voltage does not cycle to the low side check the connector and wiring to the PCM If the wiring and connector are okay the problem may be in the pin at the PCM or the driver in the computer itself Next disconnect the vacuum connection to the EGR shutoff EGRC or EVR solenoid Hook up a vacuum pump to the supply port of the EGR shutoff EGRC or EVR solenoid Fig 3 During the test you will have to supply a Connection to vacuum source Connection to EGR Valve Figure 3 constant vacuum to the port from the vacuum pump Hook up a vacuum gauge to the outlet port of the solenoid Have someone cycle the accelerator pedal The solenoid should hold vacuum in one accelerator pedal position and release vacuum in the other The release of vacuum should be in less than 2 seconds If the vacuum does not Electronic Vacuum release or Regulator EVR L X No ANCAP releases too slowly check
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